1. Field of the Invention
This invention relates to the regeneration of catalysts and more particularly a process of regenerating solid catalysts deposited with carbonaceous precipitates.
2. Prior Art
Solid catalysts used in the various chemical reactions of hydrocarbons undergo deterioration with time and such deterioration is believed to be attributable mainly to deposits of metal impurities contained in the reaction materials and also to deposits of carbonaceous precipitates resulting from hydrocarbon decomposition. The latter deposits are encountered during a variety of catalytic reaction processes employed in the petroleum or petrochemical industry such as catalytic cracking, catalytic reforming, catalytic hydrogenation, catalytic hydrogenative desulfurization, catalytic hydrogenative denitration and the like.
A most usual practice has been to remove precipitates of carbonaceous materials from the catalyst by burning them off by contact with air after the reaction is discontinued in the case where the catalyst is a fixed-bed type, or while the reaction is being carried out as in the case of catalytic cracking or reforming process.
Conventional catalyst regeneration methods using the medium of air for burning deposits of carbonaceous material off the surfaces of deteriorated catalyst may be advantageous in that the catalyst can be regenerated for reuse in a relatively short length of time if the burning is effected at elevated temperatures. However, air burning at increased temperature would often lead to thermal degradation of the catalyst. Conversely, if the burning temperature is lowered, then this will take so much more time and more amounts of air for the catalyst to be adequately regenerated.